Circuit breaker



June 13, 1939. IAKLE IN Em 2,162,534

0 IRCUIT BREAKER Filed April 1, 1933 WITNESSES: INVENTORS.

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ATTORNEY an am Patented June 13, 1939 UNITED STATES PATENT orr caCharlottcnburg,

, alaignors to Westlnghouse Electric & Manufacturing Company,

East Pittsburgh, Pa., a corporation of Pennivania Application April 1,1933. serlaiNo. 683.92! In Germany April 1, 1932 Our invention relatesto circuit breakers and is particularly suitable for use with circuitbreakers of the trip free type.

One object of our invention is to provide a circult breaker which shallnot remain in the closed position if the engaging contacts should beburned or otherwise damaged.

Another object of our invention is to provide an improved trip freecircuit breaker which shall include means for automatically opening thecircuit if the cooperating contact members become incapable of carryingthe normal circuit current without excessive heating.

Another object of our invention is to provide a double toggle linkagefor a circuit breaker where the toggle links are in straightenedposition when the circuit breaker is closed and transmit a large part ofthe opening bias to a fixed pivot so that only a small force istransmitted to the current 10 responsive latch holding one link inclosed position.

A further object of our invention is to provide an improvedtoggle-linkage, circuit breaker operating mechanism that shall beparticularly suitable for use with circuit breakers wherein safety andreliability of operation are paramount requirements.

An additional object of our invention is to provide a latching structurefor a circuit breaker .30 comprising a cylindrical latching portionnormally holding a latch member, with a notch through the cylindricallatching portion to permit movement of the latch member therethroughupon rotation of the cylindrical portion. 3:, In carrying out theseobjects'of our invention, we prefer to provide a circuit breakermechanism. which is biased to the open position by a constant forcebiasing means and which is held in the closed position partly by thereaction 10 forces resulting from the contact pressure producing means.These forces are so adjusted that any appreciable decrease in thecontact pressure, which must simultaneously reduce the reaction forceresulting therefrom, allows the biasin 45 means to open the breaker.

The features of our invention which we believe to be new are.particularly pointed' out in the appended claims. For a fullunderstanding of the principles of our invention and one method 50 ofapplying those principles, reference may be had to the accompanyingdrawing and specification, wherein;

Figure 1 is an elevational view, partly in section, of a circuit breakerembodying the principal 55 features of our i ve t he a ious structuralelements being shown in the open circuit position.

Fig. 2 is a sectional view on the line II-iI of Fig. I.

Fig. 3 is a sectional view on the line IIIIII 5 of Fig. 1.

Fig. 4 is diagrammatic view showing the various structural elements ofthe circuit breaker in the closed position, and

Fig. 5 is a diagrammatic view similar to Fig. 4 10 showing the circuitbreaker in the tripped position.

In this embodiment of our invention weprovide a pivotally mounted switchmember assemblage,

a toggle linkage operating mechanism, a trigger for restraining thetoggle linkage in the operative position, a trip device including alatch for releasably engaging the trigger, a spring for biasing themechanism to the open position, and. means which are partially dependentupon the pressure between the cooperating contact members for holdingthe mechanism closed against the action of the biasing spring.

Referring to the drawing, the circuit breaker,

- which is of the double-break, push button typ 26 includes a base I ofinsulating material upon which is mounted a pair 0! terminals 3, a pairof stationary contact supports 5, and the frame member 0 which supportsthe assemblage of switch members i, the toggle operating mechanism 8,and the trip device 0.

The assemblage of switch members 1 includes a pair of contact members Iiadapted to engage the cooperating stationary contact members it whichare mounted on the contact supports 5, 5

leaf spring supports it for the contact members I l, and a switch shaftii to which one end of each.

of the spring supports II is rigidly joined. Two

support lugs l0 and ii extend outwardly from the base member 6 andpivotally engage suitable pins 40 in the ends of the switch shaft ii. Acrank member 23 is provided for connecting the assemblage of switchmembers I with the operating mechanism l.-

As mentioned previously, the circuit breaker is of the double breaktype, the current flowing in one terminal 3, through the associatedsupport I and its contact member l3, thence through the cooperatingmoving contact ii, the spring support arm ii, the energizing coil 59 forthe trip device 9, the other spring support arm ii, and finally throughthe other contacts ii and i3 and the other support 5 to the secondterminal 8.

The operating mechanism 8 is of the toggle linkage type and includes apush button or handie member 25 of insulating material, a pair of togglelinks 21 and 29, a trigger or cradle 31' which engages one end of thetoggle linkage through a pivot pin 33, a connecting link 35 intermediatethe operating handle 25 and the toggle. links 21 and 29, and a spring 31which biases the assemblage of switch members I to is pivotally fastenedto the operating handle- 25 through the agency of the pin 45. The pin 45has the further function of acting as a stop to define the upward limitof motion of the handle 25 and its associated guide pin 39. One end ofthe toggle link 2'! is pivotally fastened to the crank member 23 by apin 41. A spring 49 is positioned about the guide pin 39 and as will beexplained later, is utilized to secure the automatic opening feature.

The trigger 31 is pivotally supported on a pin 5| which engages a lug 53projecting outwardly from the frame 6, and is provided with a portion 55ending in a latch tip for engaging the latch 51 of the trip device 9.

The trip device 9 is of the conventional solenoid type and except forthe particular type of construction disclosed is not an important partof my invention. The coil 59 is supported upon the main frame 6 and is,as mentioned before, electrically connected in series between the twospring contact arms l5 so as to be responsive to the current flowing inthe controlled circuit. A tube 6| having a slot 63 (Fig. 1) thereinextends into the center of the coil 59, and serves as a guide means forthe moving armature which is biased to the unattracted position by asuitable spring. A pin 65 which is rigidly affixed to the armatureextends through the slot 63 and engages the latch actuating member 51.

The cylindrical latch shaft 51 is pivotally mounted on two lugs 59 and Hprojecting outwardly from the frame 6, and is biased into the latchedposition by the spring 13, the projection 15 serving as a stop to limitits motion. The enlarged cylindrical end of the latch shaft 51 has alatch portion 11 which engages the cooperating portion 55 of the trigger3| and which is offset from the center of rotation of the latch properand is thus movable to release the trigger when the latch is rotated ina clockwise direction (Figs. 1, 4 and 5). The offset latch portion 11comprises the portion of the enlarged cylindrical end of the shaft 51which remains after a notch is provided in the shaft extending slightlymore than half-way through the shaft as shown on the drawing. Thestraight edge of the latch portion 55 engages the enlarged end of theshaft tangentially so that the force exerted'thereon is radially of theshaft.

The circuit breaker is closed by a downward pressure on the operatinghandle 25, the spring 49 being compressed and tending to move theoperating handle and the knee pivot pin 43 upwardly. The toggle linkageis moved from the position shown in Figure 1 to the position shown inFigure 4. During this movement the knee pivot pin is moved below thestraight line position, thus locking the contacts closed as is done byconventional toggle operated mechanism. As

the handle 25 is moveddownwardiy, the crank arm 23 is rotatedcounterclockwise; the trigger 3| is likewise rotated but in theclockwise direction, the end 55 engaging the latch portion i? near theend of the closing operation.

The rotation of the crank arm 23 causes a tensioning of the spring 31and, by rotating the switch shift l1, causes the movable contactmembers'll to engage the stationary contact members l3 thereby bendingthe leaf spring contact supports l5 tosupply the necessary contactpressure. The reactive force from this stressing oi the contact supportsl5 acts through the crank arm 23 and the toggle link 2? as a pressure onthe knee pivot pin 43 of the toggle linkage, and,

because of the over center or locked position of the linkage, will havea component opposing the spring 49. This component in combination withthe similar component resulting from the tensioning of the spring 31, isof suiiicient magnitude, when adequate contact pressure exists betweenthe cooperating contact members H and I3, to hold the circuit breakerclosed.

However, if excessive Wear, burning or other damaging agencies have soaltered the contact members that proper engagement therebetween is notobtained when the operating handle 5 is moved to the closed position,the circuit breaker will open automatically as soon as the handle isreleased, due to the inadequacy of the force component balancing theopening spring 49. This feature is of very great value in preventingcontinued use of damaged switches wherein the insufiicient contactpressure may cause enough heating to constitute a dangerous fire hazard.

The opening operation under these conditions is substantially thereverse of the closing operation. The spring 49 lifts the knee pivot pin43 above the center line of the link, the toggle then collapses upwardlydrawing the trigger 3i with it, the spring 31 acting through the crankmember to move the contacts to the open position. The projection 79serves as a stop for limiting the rotation of the crank member 23.

It is important to note that movement of the assemblage of switchmembers 1 beyond a predetermined point is equally effective. in securingautomatic opening of the circuit. This follows from the fact that thedistance which the knee pivot pin 43 moves beneath the center line ofthe toggle is proportional to the force opposing the biasing action ofthe spring 59. Thus, if the assemblage of switch members I rotatessufliciently far to reduce this distance below the minimum" required tobalance the kneebiasing force the breaker will not remain in the closedcircuit position when the operating handle 25 is released.

In the event of an overload or other predetermined electrical condition,the coil 59 of the trip device becomes energized sufiiciently to attractits associated armature. The pin 65 (Fig. 3) engages the latch actuatingmember 51 and, by rotating the latch against its biasing spring 13,causes the portion 11 to disengage the trigger 3i. The entire togglelinkage is then free to move to the open position under the influence ofthe stressed spring supports l5 and the spring 31. If the handle is notheld down the spring 49 returns the various parts of the mechanism tothe position shown in Figure 1. If an attempt is made to hold thecircuit breaker closed the mechanism moves, following the trippingoperation, to the position shown in Figure 5, the mechanism beingentirely trip free.

the operating handle 25 away from thebase l-..

The release mechanism, however, assures the rapid separation oi theengaging contact members and is the preferred method of operation.

It will thus be seen that we have disclosed an improved circuit breakeroperating mechanism which automatically opens the circuit if thecontact, members are burned or damaged, or if the contact pressure isinadequate to prevent dangerous overheating, and in addition, we havedisclosed how this feature of our invention may be embodied into acircuit breaker oi the trip-tree Further, we have disclosed a novelcircuit breaker operating mechanism of the toggle linkage type which ismore reliable and more satisiactory in operation than the previouslyknown devices.

. The prin ciples which' we have disclosed are capable of wideapplication to circuit breakers generally, and it is our desire that thelanguage of the accompanying claims shall beaccorded the.

broadest reasonable construction, and that our invention shall be imitedonly by what is cxplicitly stated in the claims and by the prior art.

- I claim as my invention:

1. In a circuit interrupter, a stationary contact member, a movableswitch means including a contact member for cooperating therewith toopen and close the electrical circuit through said interrupter, springmeans for supplying contact pressure between said cooperating memberswhen said interrupter is in the closed position, and an operatingmechanism for actuating said switch means, said operating mechanismincluding a toggle linkage, means biasing the knee of said linkage tothe open circuit position, and means responsive to the contact pressurebetween sad m cooperating members for holding the knee of said toggle inthe closed circuit position against said biasing means, said holdingmeans being releasable and causing the movable contact member to move toopen circuit position upon a predcterg mined decrease in contactpressure between said cooperating members.

2. In a circuit interrupter, a stationary contact,

cooperating with said stationary .contact for opening and closing theelectrical circuit through said interrupter, and an operating mechanismfor actuating said switch member, said operating mechanism including atoggle linkage, means for biasing the knee of said toggle to the opencircuit position, and means operable upon change in the contact pressurebetween said .contacts to cause said biasing means to. move the knee ofsaid toggle and said switch member to open circuit position. 3. In acircuit interrupter, a butt contact member, a movable switch meansincluding a contact member for making butt engagement with said buttcontact and movable to open and close the electrical circuit throughsaid interrupter, an operating mechanism for actuating said switchmeans, a spring for biasing said switch means to the open position, saidoperating mechanism including means separate from said butt contact-members operable to locksaid switch means in the closed circuitposition, and said locking means being operable only when there is apredetermined contact pressure between said butt contact members.

4. In a circuit interrupter, a stationary contact member, a pivotallysupported switch member, including a contact and a. leaf spring supportfor said contact, for cooperating therewith to open and to close theelectrical circuit through said interrupter, and an operating mechanismfor actuating said switch member, said operating mechanism including apair or toggle links pivotally joined together at one end by a kneepivot pin, the other end of one link operatively engaging said switchmember and the other end or the second link engaging a releasabletrigger normally held by current responsive means, spring means biasingsaid knee pivot pin to the open circuit position, and means responsiveto the movement of said switch member beyond a predetermined point forholding the knee of said toggle in the closed circuit position againstsaid biasing means, said knee pivot pin, when said interrupter is in theclosed circuit position, being free to move under the biasing action ofsaid spring .to the open circuit position when released by said holdingmeans.

5. In a circuit interrupter, relatively movable contact means foropening and closing the electrical circuit through said interrupter, oneoi said contact means including a switch member, spring means biasingsaid switch member to the open circuit position when said interrupter isin the closed circuit position, and an operating mechanism for actuatingsaid switch member, said operating mechanism including a toggle linkageand a bell crank having one arm pivoted to one end of said togglelinkage, current responsive means normally holding the other arm of saidbell crank, resilient means for biasing the knee of said toggle linkageto collapsed open circuit position when said interrupter is in' theclosed circuit positiomand means whereby said spring means biasing saidswitch member to the open circuit position holds the knee of said togglelinkage in the closed circuit position against said knee biasing meanswith; said toggle links and said arm in straightened position with eachmaking only a relatively small angle with the line between the pointsconnected thereby, and said current responsive means being movable torelease said bell crank and cause the collapse of said toggle linkage inthe direction in which it is a switch member having a moving contact torbiased by said knee biasing means.

6. In a circuit interrupter, a stationary contact member, a pivotallysupported switch member cooperating therewith to open and to close theelectrical circuit through said interrupter, spring means biasingsaidswitch member to the open circuit position when said interrupter isin the closed circuit position, an electro-responsive trip device, andan operating mechanism for actuat ing said switch member, said operatingmechanism including a pair 'of toggle links'pivotally joined together atone end by a knee pivot pin, the other end of one link operativelyengaging said switch member and the other end or the circuit position,and means whereby the reactive force of said spring means biasing saidswitch member to the open circuit position holds said knee pivot pin inthe closed circuit position against said spring biasing means acting onsaid knee pivot pin, said knee pivot pin, when in the closed circuitposition, being free to move under the biasing action of said springmeans to the open circuit position when the reactive force of the saidbiasing means falls below a certain predetermined value.

7. In a circuit interrupter, a stationary contact member, a movablecontact member for cooperating therewith to open and to close theelectrical circuit through the interrupter, resilient means supplying apredetermined pressure between the cooperating contact surfaces of saidcontact members, the reaction force of said resilient pressure securingmeans biasing said movable contact member toward the open circuitposition when said interrupter is in the closed circuit position, and anoperating mechanism for actuating said contact means, said operatingmechanism including a toggle linkage the knee of which is adapted tomove to the over-center po sition when said switch means is moved to theclosed circuit position, a movable member to which one end of the togglelinkage is pivoted, said movable member being biased to move to atripped position by the force of said resilient means biasing themovable contact to open circuit position, current responsive meansnormally retaining said movable member against said bias and beingreleasable to permit said movable contact to move to open circuitposition, and a spring means for biasing the knee of said linkage towardthe open circuit position, said resilient means, said spring, and saidlinkage being so correlated that the reaction force of said resilientmeans holds said linkage in the over-center,-

closed circuit position, against the biasing force of 'said spring, whensaid circuit interrupter is in the closed circuit position and normalcontact pressure exists between said cooperating contact surfaces, andbeing so correlated that when said contact pressure falls below apredetermined value said reaction force becomes incapable of holdingsaid toggle linkage against movement toward the open circuit positionunder the biasing action of said spring.

8. In a circuit interrupter, a contact actuating member movable to anopen and to a closed circuit position, means normally biasing saidmember to the open circuit position, a contact supported upon saidcontact actuating member, means biasing said contact toward the closedcircuit position, at least when said interrupter is in the closedcircuit position, means for holding said contact actuating member in theclosed circuit position against the force of said first mentionedbiasing means, and means responsive to the magnitude-of the forcebiasing said contact to the closed circuit position for releasing saidholding means when the magnitude of the force biasing said contact tothe closed circuit position becomes less than a predetermined amount.

9. In a circuit interrupter, a contact actuating member movable to anopen and to a closed circuit position, means normally biasing saidmember to the open circuit position, a contact supported upon saidcontact actuating member, spring means intermediate said contact andsaid contact actuating member which serves to bias said contact towardthe closed circuit position, at least when said interrupter is in theclosed circuit position, means for holding said contact actuating memberin the closed circuit position against the reaction force of said springmeans, and means responsive to the magnitude of the force exerted bysaid spring means tending to bias said contact to the closed circuitposition for releasing said holding means when the magnitude of thatforce becomes less than a. predetermined amount.

10. In a. circuit interrupter, a contact actuating member movable to anopen and to a closed circuit position, means normally biasing saidmember to the open circuit position, a stationary contact, a movablecontact for cooperating therewith which is supported upon said contactactuating member, resilient means for biasing said movable contacttoward said stationary contact at least when said interrupter is in theclosed circuit position, said cooperating contacts engaging each otherwith a butt type engagement when said interrupter is in the closedcircuit position, means for holding said contact actuating member in theclosed circuit position against the force of said first-mentionedbiasing means, and means responsive to the magnitude of the forcebiasing said movable contact toward said stationary contact forreleasing said holding means when the magnitude of the force biasingsaid contacts into engagement with each other becomes less than apredetermined amount.

11. In a circuit interrupter, a stationary contact member, a movableswitch means including a contact member for cooperating therewith toopen and close the electrical circuit through said interrupter, springmeans for supplying contact pressure between said cooperating memberswhen said interrupter is in the closed position, a second spring meansbiasing said movable switch means to open circuit position, an'operatingmechanism for actuating said switch means, said operating mechanismincluding a toggle linkage connected to said switch means at all timesand movable upon each movement of said switch means, a third springmeans biasing the knee of said link-,

age to the open circuit position, said operating mechanism transmittingone component of the force exerted by each of the first two of saidspring means to said knee of the toggle linkage for holding the knee ofsaid. linkage against movement to open circuit position by said thirdspring means, and the component of force exerted n the knee of saidlinkage by said second spring means alone being insuflicient to preventits movement to open circuit position whereby said third spring meansmoves the knee of the toggle to open circuit position upon apredetermined decrease in the force exerted by the first spring meansfor supplying contact pressure, and current responsive means normally inlatching engagement with a part of said operating mecha nism forpreventing said second spring means from automatically moving saidswitch means to open the circuit and movable out of engagement with saidoperating mechanism for initiating movement of said operating mechanismand said switch means to open circuit position.

12. ha circuit interrupter, a pair of relatively movable contacts, amovable switch member for moving one of said contacts to open and closethe circuit, spring means biasing said switch member to move to openposition and biasing said contacts into pressure engagement, operatingmeans for said switch member including three links, one

of said links being pivoted to said switch member at a movable pointthereon, another of said links being pivoted at a fixed point, and thethird of said links being pivotally connected between the first twolinks, means for manually moving one of said links to move said switchmember to closed position, said links when in the closed position havingthe pivot points connecting them only a small distance away irom thestraight line between the point at which said one link is pivoted to theswitch member and said fixed pivot point whereby the iorce o! the biasoi said switch member is largely transmitted to said fixed pivot pointand there is only a small force tending to move the pivot pointsconnecting the links away from said straight line, means providing astop preventing the force of said bias from moving one of the pivotpoints connecting the links out of its closed position adjacent to saidstraight line, spring means biasing the last said pivot point of thelinks to move away from said stop and cause opening of the contacts, thelast said spring means becoming eilective to cause opening of thecontacts after there has been a predetermined decrease in the pressurebetween said contacts, latching means normally engaging and holding oneof said links to prevent the force of the first said biasing means frommoving the other pivot point connecting the links out of its closedposition adjacent said straight line, and said latching means beingmovable upon the occurrence ot a predetermined electrical condition todisengage said link and permit the first said biasing means to move theswitch member to open the circuit.

13. In a circuit interrupter, a pair of relatively movable contacts, aswitch member for moving one of said contacts to open and close thecircult, spring means biasing said switch member to open position,operating means for said switch member including three links, one ofsaid links being pivoted to said switch member at a point movable withthe switch member, another oi said links being pivoted at a fixed point,and the third of said links being pivotally connected at each end to oneof the first two links forming two knee pivot points each movable tocollapsed position, means for manually moving one of said links to movesaid switch member to closed position, said links when in the closedposition having the knee pivot points connecting them not more than asmall distance away from the straight line between the point at whichsaid one link is pivoted to the switch member and said fixed pivot pointwhereby the force of the bias of said switch member is largelytransmitted to said fixed pivot point and there is only a small forcetending to move the knee pivot points connecting the links away fromsaid straight line to collapsed position, means providing a stoppreventing the force of said bias from moving one of the knee pivotpoints connecting the links from its closed position adjacent to saidstraight line to collapsed position, a latch member normally engagingand holding one of said links to prevent the force of said bias frommoving the other of the knee pivot points from its closed positionadjacent said straight line to collapsed position, and said latchmember'being movable upon the occurrence of a predetermined electricalcondition to disengage said link and permit the biasing means to movethe switch member to open the circuit.

14. In a circuit breaker, a pair of relatively movable contacts, aswitching member for moving one of said contacts to open and close thecircuit, spring means biasing said switching member to move to openposition, operating means for said switching member including threelinks forming a double toggle, one of said links being pivoted to saidswitching member at a point thereon which is movable with the switchingmember upon every movement thereof, another or said links being pivotedat a fixed point, and the third oi said links being pivotally connectedat each of its ends to one 0! the first two links to form the two kneesof the double toggle, actuating means by which one of said links ismovable to cause normal movement of said switching member to both openand close the breaker, said double toggle when in closed position beingin substantially a straight line with one knee thereof under-set,current responsive latching means normally engaging and holding one ofsaid links to prevent said under-set knee of the toggle from moving tocollapsed position, said latching means being disengageable upon theoccurrence of an abnormal condition to permit said knee of the toggle tomove to collapsed position and cause movement of said switching memberto open position, stop means holding the other knee of the toggle inover-set position when the breaker is closed, and the last said kneebeing movable between said over-set and collapsed positions uponmovement of .said actuating means to normally open and close the breakerwithout disengagement of said latching means.

15. In a circuit breaker, a pair of relatively movable contacts, aswitching member for moving one of said contacts to open and close thecircuit, spring means biasing said switching member to move to openposition, operating means for said as switching member including a pairof pivoted toggle links and a bell crank pivotally mounted at its apexand having one arm pivoted to one end of said pair of toggle links toform a double toggle therewith, actuating means by which one of saidtoggle links is movable to cause normal movement of said switchingmember to both open and close the breaker, said double toggle when inclosed position opposing opening movement of said switching member andbeing in a substantially straight line so as to transmit most of theforce biasing said switching member through the double toggle to a fixedpoint and so as to leave only small forces tending to collapse thedouble toggle at its knee pivots, current responsive latching meansnormally engaging and holding the other arm of the bell crank to preventthe knee pivot between the bell crank and the first said pair 01' togglelinks from moving to collapsed position, said latching means beingdisengageable upon the occurrence of an abnormal condition to permit thelast said knee pivot to move to collapsed position and cause movement ofsaid switching member to open position, stop means holding the kneepivot of the first said pair of toggle links in over-set position whenthe breaker is closed, and the last said knee pivot being movablebetween over-set and collapsed positions upon movement of said actuatingmeans to normally open and close the breaker without disengagement ofsaid latching means from said bell crank.

16. In a circuit breaker, a pair of relatively movable contacts, aswitching member for moving one of said contacts to open and close thecircuit, spring means biasing said switching member to move to openposition, operating means for said switching member including a pair ofpivoted toggle links and a bell crank pivotally mounted at its apex andhaving one arm pivoted to one end of said pair of toggle links to form adouble toggle therewith, actuating means by which one of said togglelinks is movable to cause normal movement of said switching member toboth open and close the breaker, said double toggle when in closedposition opposing opening movement of said switching member and being ina substantially straight line so as to transmit most of the forcebiasing said switching member through the double toggle to a fixed pointand so as to leave only small forces tending to collapse thedoubletoggle at its knee pivots, current responsive latching meansnormally engaging and holding the other arm of the bell crank to prevent the knee pivot between the bell crank and the first said pair oftoggle links from moving to collapsed position, said latching meansbeing disengageable upon the occurrence of an abnormal condition topermit the last said knee pivot to move to collapsed position and causemovement of said switching member to open position, stop means holdingthe knee pivot of the first said pair of toggle links in over-setposition when the breaker. is closed, and the last said knee pivot beingmovable between over-set and collapsed positions upon movement of saidactuating means to normally open and close the breaker withoutdisengagement of said latching means from said bell crank, and means forcausing the knee pivot of the first said pair of toggle links to movefrom over-set to collapsed position upon relase of said bell crank byits latching means to cause return of said actuating means to openposition and to cause re-engagementof said bell crankwith its latchingmeans.

17. In a trip device for a circuit breaker, the combination of arotatable trip shaft, and a pivoted latching member biased for movementfrom a latching to a releasing position having a latch tip normallyengaging said shaft to restrain said latching member in said latchingposition, the pivot of said latching member and the axis of said shaftbeing so related that said latch tip tangentially engages said shaft toexert a substantially radial force thereon, whereby substantially norotative movement is exerted on said shaft by said latching member, saidtrip shaft having a transversely extending notch therein through whichsaid latch tip moves to said releasing position upon rotation of saidtrip shaft to a predetermined position.

18. In a trip device for a circuit breaker, the combination of acylindrical trip shaft mounted for rotation about a longitudinal axis,and a pivoted latching member biased for movement from a latching to areleasing position having a latch tip normally engaging the periphery ofsaid shaft to restrain said latching member in said latching position,the pivot of said latching member and said axis of said shaft being sorelated that said latch tip tangentially engages the periphery of saidshaft to exert a substantially radial force thereon, wherebysubstantially no rotative moment is exerted on said shaft by saidlatching member, said trip shaft having a transversely extending notchtherein through which said latch tip moves to said releasing positionupon rotation of said trip shaft to a predetermined position.

19. In a trip device for a circuit breaker, the combination of arotatable trip shaft, and a pivoted latching member biased for movementfrom a latching to a releasing position having a latch tip normallyengaging said shaft to restrain said latching member in said latchingposition, the pivot of said latching member being so related to saidshaft that said latch tip moves along an are passing substantiallythrough the axis of said shaft, whereby substantially no rotative momentis exerted on said shaft by said latching member, said shaft having atransverse slot extending slightly more than half-way through said shaftso that upon rotation of said shaft to a predetermined position saidlatch tip is released for movement along said are to said releasingposition.

20. In a trip device for a circuit breaker, the combination of acylindrical trip shaft mounted for rotation about a longitudinal axis,and a pivoted latching member biased for movement from a latching to areleasing position having a latch tip normally engaging the periphery ofsaid shaft to restrain said latching member in said latching position,the pivot of said latching member being so related to said axis thatsaid latch tip moves along an arc intersecting said axis, wherebysubstantially no rotative moment is exerted on said shaft by saidlatching member, said shaft having a transverse notch therein extendingmore than halfway through said shaft so that said latch tip may freelymove along said are when said shaft is rotated to a predeterminedposition to release said latching member for movement to said releasingposition.

PAUL KLEIN. KURT WULS'I'EN.

DISCLAIMER 2,162,534.Paul Klein, Berlin, and Kurt Wulsten,Berlin-Charlottenburg,

Patent dated June 13, 1939. Disclaimer filed Decem- CIRCUIT BREAKER.

Germany.

ber26, 1940, by the assignee, Westinghouse Electric cf: ManufacturingCompany. Hereb enters this disclaimer to claims 17, 18, 19 and 20 of thepatent.

[ ial Gazette January 28, 1941.]

